Apparatus for manufacturing leaf springs having a tapered end portion

ABSTRACT

An apparatus comprises a furnace to heat a metal band, rolling mill rolls forming a plurality of tapers at portions of the heated metal band, shearing means to divide the tapered metal band into a plurality of leaf spring units with opposite tapered ends.

United States Patent [191 Shiguma et al.

[ APPARATUS FOR MANUFACTURING LEAF SPRINGS HAVING A TAPERED END PORTION[75] Inventors: I-Ieijiro Shiguma; Shigekazu Suzuki,

both of Yokohama, Japan [73] Assignee: NHK Spring Co., Ltd.,

Yokohama-shi, Japan [22] Filed: July 19, 1973 [21] Appl. No.: 380,580

[30] Foreign Application Priority Data July 20, 1972 Japan 47-72876 July12, 1973 Japan 48-78813 [52] US. Cl 72/185, 72/240, 29/173 [51] Int. Cl[58] Field of Search 72/240, 185, 184, 203,

[ June 28,1974

[56] References Cited UNITED STATES PATENTS 2,156,584 5/1939 DeBenedetti 72/240 3,081,653 3/1963 Kincaid 72/8 3,339,908 9/1967Komamitsky 29/173 X 3,534,576 10/1970 Abernathy et a1. 72/240 PrimaryExaminer-Milton s. Mehr Attorney, Agent, or Firm-Kemon, Palmer &Estabrook [5 7] ABSTRACT An apparatus comprises a furnace to heat ametal band, rolling mill rolls forming a plurality of tapers at portionsof the heated metal band, shearing means to divide the tapered metalband into a plurality of leaf spring units with opposite tapered ends.

9 Clains, 18 Drawing Figures PAINTED-111828 I914 1 3; 820.373

sum 1 or 5 Flg. 1

10 A 1 METAL PWHEATING BAND E I TAPER SHEAR- C NTER FORMING me: E g mSTEP STEP 7 i I 1 B p -c 0 PATENIEU JUN 28 I974 sum 2 or 5 m mm mm mm.um i a a: n. w Q q H JG. o H \D MN\\ ON 5 ON Om/ ON Om ON MN mm mm mmmm N APPARATUS FOR MANUFACTURING LEAF SPRINGS HAVING A TAPERED ENDPORTION This invention relates to an apparatus for manufacturing leafsprings having tapered end portions.

Leaf springs used in, for example, a vehicle are formed of an elongatedmetal plate whose end portions are tapered. To manufacture such leafsprings, there is provided an apparatus comprising a shear for cutting along metal band for every predetermined length to provide plate springunits, a punch for forming a center hole in the plate spring unit, aheater for heating one or both end portions of the plate spring unit,and means for tapering the heated end portion of the plate spring unit.

In such a conventional apparatus, it is required to provide means fortransferring individual plate spring units from one step to another andmeans for fixing the plate spring unit when subject to treatment,causing the apparatus to be bulky and complex in construction. Moreover,leaf springs manufactured with such a conventional apparatus are notunifonn in quality.

The object of this invention is to provide an apparatus which is compactand simple in construction and which is capable of producing leafsprings of high quality and high reliability.

The present invention can be more fully understood from the followingdetailed description when taken in connection with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic illustration of method for manufacturing leafsprings using an apparatus in accordance with this invention;

FIGS. 2A to 2C are side and plan views of the leaf springs produced ateach step shown in FIG. 1;

FIGS. 3 and 4 are respectively a plan view and a side view of theapparatus in accordance with this invention;

FIG. 5 is a schematic illustration of the method for manufacturing leafsprings using the apparatus shown in FIGS. 3 and 4;

FIG. 6 is a block diagram of a control circuit for controlling a rollingmill roll used in the apparatus shown in FIGS. 3 and 4;

FIG. 7 illustrates the dimensions of a leaf spring manufactured with theapparatus under control of the control circuit;

FIG. 8 shows an enlarged view of .part of the leaf spring shown in FIG.7;

FIGS. 9A to 9D are sectional views of leaf springs produced with theapparatus; and

FIGS. 10A to 10D are perspective views of the leaf springs which can beformed using another apparatus in accordance with this invention.

Referring now more in detail to the drawings, there is schematicallyillustrated in FIG. 1 method for manufacturing leaf springs using anapparatus in accordance with this invention.

An elongated metal band 10 is heated to a predetermined temperature, forexample 900C, at heating step A. A heating furnace providing a furnacetemperature of 900C may be used for this heat treatment. The metal band10 heated is transferred to taper forming step B to be pressed andtapered at predetermined intervals in the form as shown in FIG. 2A. Aportion 12 is defined by opposite tapered portions 11 to form a leafspring unit. Then, the metal band 10 is fed to shearing step C to be cutalong the broken lines (FIG. 2A)

between adjacent tapered portions so that the leaf spring-units 12 areseparated from each other (FIG. 2B). If required, the leaf spring unit12 is reheated and fed to center hole forming step D to be bored with acenter hole 13, thereby providing a complete. leaf spring unit 12 (FIG.2C). The center hole forming step D, however, can be eliminated orcarried out prior to, for example, the step C.

An apparatus of this invention for manufacturing leaf springs accordingto the steps mentioned above may be designated to continuously carry outthe steps. Therefore, the apparatus may be made compact and simple inconstruction and is capable of producing leaf springs of high qualityand high reliability.

FIGS. 3 and 4 illustrate an apparatus in accordance with this inventionand the operation method thereof. The apparatus is provided with aroller table 20 along which a metal band and leaf spring units shearedapart from the metal band are fed. The front portions of this table 20is so arranged as to introduce a metal band into a heating furnace 21such as a well known lateral furnace. Furnace temperature of thisheating furnace 21 is preferably set at about 900C so that the metalband may easily be rolled. Disposed following the heating furnace 21 isa taper forming unit 22 which includes a pair of rolling mill rolls 23and 24, and two pairs of pinch rolls 25 and 26 respectively arranged atthe input and output sides of the rolls 23 and 24. Each leaf spring unitmay be tapered at both end portions by pressing the leaf spring unitbetween rolls 23, 24 while the upper roll 23 moves vertically. The leafspring unit, now tapered, is fed along the roller table to thesubsequent step, shearing step C. The step C is carried out by a pair ofshearing blades 27 and 28 arranged on the upper and lower sides of theroller table, respectively. The upper blade 27 is hydraulically drivenin a vertical direction against the stationary lower blade 28 to cut offthe metal band at a portion between the adjacent tapered portionsthereby obtaining discrete leaf spring units.

The roller table 20 is divided at a rear portion into two tables 20a.Disposed at the junction is a separating means 29 which selectivelyfeeds the leaf spring units to the tables 20a. The leaf spring units arefed to and reheated by reheating means 30 on the tables 20a. Then, theleaf spring units are fed to assemblies of punches 31 and dies 32mounted on the tables 20a so as to carry out the center hole formingstep D. The punches 31 may be vertically moved to punch the leaf springunit supported by the dies 32 so that a center hole may be formed at thecenter of the leaf spring unit.

Referring now to FIGS. 6 to 9' the relationship between the rolling millrolls and the pinch rolls in the taper forming step is detailed below.

As shown in FIG. 6, a pulse generator is operatively connected to one ofthe pinch rolls 25 and other pulse generators 41a and 41b are connectedto the lower and upper pinch rolls 26 respectively. Each of the pulsegenerators 40 and 41a produces a pulse signal according to the rotationof the corresponding roll and the pulse generator 41b produces a pulsesignal according to the vertical movement of the upper roll 26 or eachwhen the upper roll 26 vertically moves through a predetermineddistance. The pulse generators 40, 41a and 41b are connected to theoutput terminals of a logic circuit 42 which stores the information onthe dimensions of a leaf spring to be formed, that is, length of thefront tapered portion 11a of the leaf spring unit, thickness t at thefront end, length l of the rear tapered portion 11b, thickness t at therear end, overall length L and thickness T at the center portion (seeFIGS. 7 and 8). The output terminal of the logic circuit 42 is connectedto a pulse motor 43 so that the motor 43 may be rotated according to theoutput pulse signal of the logic circuit 42. The motor 43 drives a screwdown mechanism 44 which, in turn, drives the upper roll 23 in a verticaldirection.

In this embodiment, a pulse signal is generated from the pulse generator40 each time a predetermined length of the metal band has passed throughbetween the rolls 25 and then the pulse signal is applied to the logiccircuit 42 so as to be processed depending on the preset value of thedimensions of the leaf spring stored in the logic circuit 42. An outputpulse signal is generated from the circuit 42 corresponding to its inputsig nals and then applied to the motor 43 so that the motor 43 may bedriven and vertically move the upper roll 23 to roll the metal band intoa predetermined shape. Where, for example, the leaf spring unit istapered at the front end portion, first the upper roll 23 is set at theheight equal to the thickness 1? at the front end of the leaf spring andthen the upper roll 23 is upwardly moved through Ah each time the metalband advances through Al. The upward movement of the roll 23 may bestopped when the formation of the taper is completed. Likewise, thetaper at the rear end portion of this leaf spring unit may be formedafter the metal strip moves through a predetermined distance.

The pinch rolls 26 are provided to check that the leaf spring unit istapered in a desired shape. When the tapered portion formed by therolling rolls 23 and 24 passes through between the pinch rolls 26, thelower pinch roll 26 rotates so that the pulse generator 41a may producea pulse signal each time the leaf spring unit advances through adistance Al. At the same time, the pulse generator 41b may produce apulse signal each time the upper pinch roll 26 vertically moves througha distance Al. Both pulse signals generated from the pulse generators41a and 41b are applied to the logic circuit 42 and compared with thepreset values stored therein. If the leaf spring is not tapered in apredetermined form, the output signal from the logic circuit 42 iscorrected according to the difference between said both pulse signalsand the preset values stored in the circuit 42. The corrected outputsignal is applied to the pulse motor 43 so as to control the movement ofthe roll 23 thereby to roll the metal strip in a predetermined form.

With the apparatus mentioned above, it is possible to taper the endportion of the leaf spring in a linear or curved form by suitablychoosing the preset values of the dimensions of the leaf spring. Theinput and output side tapered portions may be formed symmetrically orasymmetrically.

FIGS. 9A to 9D illustrate leaf springs which may be made by theapparatus of this invention. A leaf spring shown in FIG. 9A has endportions 11a, 11b linearly and symmetrically tapered with respect to thecrosswise central line, a leaf spring of FIG. 93 has linearly taperedassymmetrical end portions 11a, 11b, a leaf spring of FIG. 9C hassymmetrical end portions 11a, 1 lb tapered with the same curvature R anda leaf spring of FIG. 9D has asymmetrical end portions 11a, 11b taperedwith different curvatures R and R respectively.

In the embodiment above mentioned, the lower roll 24 is stationary butit is possible to move the lower rolling mill roll in a verticaldirection so as to form leaf springs shown in FIGS. 10A to 10D. A leafspring shown in FIG. 10A has both end portions 11a, 11b linearly andsymmetrically tapered with respect to the crosswise central line on bothupper and lower sides, a leaf spring of FIG. 10B is similar to thatshown in FIG. 10A except that its both end portions 11a, 11b areasymmetrically tapered, a leaf spring of FIG. 10C has both-end portions11a, 1 lb symmetrically tapered with the same curvature relative to thecrosswise central line on both upper and lower sides, and a leaf springof FIG. 10D is similar to that shown in FIG. 10C except that its bothend portions 11a, 1 lb are asymmetrically tapered.

What we claim is:

1. An apparatus for manufacturing leaf springs having a tapered endportion comprising: heating means to heat a metal band, taper formingmeans for forming a plurality of tapers at portions of the heatedmetal'band disposed in predetermined intervals, shearing means to dividethe tapered metal band into a plurality of leaf spring units having atapered end, and moving means for moving the metal band to shearingmeans from the heating means through the taper forming means.

2. An apparatus according to claim 1 which further includes center holeforming means for forming a center hole in each of leaf spring units.

3. An apparatus according to' claim 2 which further includes reheatingmeans for reheating the leaf spring unit to be provided with a .centerhole.

4. An apparatus according to claim 2 wherein the center hole formingmeans includes a vertically movable punch and a stationary die, the leafspring units fed between the punch and die.

5. An apparatus according to claim 1 wherein the heating means includesa lateral furnace through which the metal band is moved.

6. An apparatus according to claim 1 wherein the taper forming meansincludes a pair of rolling mill rolls at least one of which isvertically movable.

7. An apparatus according to claim 6 which further includes controlmeans for automatically moving the rolling mill roll in a verticaldirection to form the tapered portion.

8. An apparatus according to claim 7 wherein the control means includesa pair of first pinch rolls between the heating means and rolling millrolls, a first pulse generator connected to the pinch rolls to produce apulse signal each time a predetermined length of the metal band ispassed between the pinch rolls, a logic circuit storing the informationon the dimensions of a leaf spring to be formed and receiving the pulsesignal from the first pulse generator, so that the pulse signal isprocessed depending on the preset value of the dimensions of the leafspring whereby the logic circuit generates an output pulse correspondingto the pulse signal from the first pulse generator, a pulse motorconnected to the logic circuit to be driven by the pulse signal from thelogic circuit and a screw down mechanism driven by the pulse motor tovertically move one roll of said rolling mill rolls.

9. An apparatus according to claim 8 which further includes a pair ofsecond pinch rolls disposed between the rolling mill rolls and shearingmeans, one of the second pinch rolls being vertically movable in contactwith the one side of the leaf spring unit where the taper is the secondpinch rolls, the second and third pulse generators respectivelyconnected to the logic circuit in which the pulse signals from thesecond and third pulse generators are set to be processed depending onthe preset value of the dimensions to correct the pulse signal from thelogic circuit.

1. An apparatus for manufacturing leaf springs having a tapered endportion comprising: heating means to heat a metal band, taper formingmeans for forming a plurality of tapers at portions of the heated metalband disposed in predetermined intervals, shearing means to divide thetapered metal band into a plurality of leaf spring units having atapered end, and moving means for moving the metal band to shearingmeans from the heating means through the taper forming means.
 2. Anapparatus according to claim 1 which further includes center holeforming means for forming a center hole in each of leaf spring units. 3.An apparatus according to claim 2 which further includes reheating meansfor reheating the leaf spring unit to be provided with a center hole. 4.An apparatus according to claim 2 wherein the center hole forming meansincludes a vertically movable punch and a stationary die, the leafspring units fed between the punch and die.
 5. An apparatus according toclaim 1 wherein the heating means includes a lateral furnace throughwhich the metal band is moved.
 6. An apparatus according to claim 1wherein the taper forming means includes a pair of rolling mill rolls atleast one of which is vertically movable.
 7. An apparatus according toclaim 6 which further includes control means for automatically movingthe rolling mill roll in a vertical direction to form the taperedportion.
 8. An apparatus according to claim 7 wherein the control meansincludes a pair of first pinch rolls between the heating means androlling mill rolls, a first pulse generator connected to the pinch rollsto produce a pulse signal each time a predetermined length of the metalband is passed between the pinch rolls, a logic circuit storing theinformation on the dimensions of a leaf spring to be formed andreceiving the pulse signal from the first pulse generator, so that thepulse signal is processed depending on the preset value of thedimensions of the leaf spring whereby the logic circuit generates anoutput pulse corresponding to the pulse signal from the first pulsegenerator, a pulse motor connected to the logic circuit to be driven bythe pulse signal from the logic circuit and a screw down mechanismdriven by the pulse motor to vertically move one roll of said rollingmill rolls.
 9. An apparatus according to claim 8 which further includesa pair of second pinch rolls disposed between the rolling mill rolls andshearing means, one of the second pinch rolls being vertically movablein contact with the one side of the leaf spring unit where the taper isformed, a second pulse generator connected to said one second pinch rollto produce a pulse signal each time said one second pinch rollvertically moves through a predetermined distance, and a third pulsegenerator connected to the other of said second pinch rolls to produce apulse signal each time a predetermined length of the leaf spring unit ispassed between the second pinch rolls, the second and third pulsegenerators respectively connected to the logic circuit in which thepulse signals from the second and third pulse generators are set to beprocessed depending on the preset value of the dimensions to correct thepulse signal from the logic circuit.